Effects of Season and Low Temperature on Polypeptides from Thylakoids Isolated from Chloroplasts of Pinus silvestris

Thylakoids isolated from pine chloroplasts were solubilized by sodium dodecyl sulphate and the polypeptides were separated by polyacrylamide gel electrophoresis. The chlorophyll-protein complexes, P700-CPa₁ and LH-CPa/b, had apparent molecular weights of 92,000 and 25,000, respectively. When the chlorophyll of P700-CPa₁ was extracted or photobleached, the apoprotein of P700-CPa₁ appeared as a pronounced peak in the polypeptide scan profile. The molecular weight of the apoprotein was 70,000. During autumn and winter the complex P700-CPa₁ was destroyed. This was primarily caused by bleaching of chlorophyll, as the 70,000 apoprotein increased in the scan profile when the complex P700-CPa₁ decreased. The winter destruction of P700-CPa₁ was less pronounced in old needles than in young. Freezing of frost-hardened seedlings did not change the polypeptide scan profile, unless the temperature was lowered below the frost-killing point followed by thawing and post-treatment in light or darkness above 0°C. Again the main destruction occurred in the P700-CPa₁ complex, but in this case no significant increase of the apoprotein was observed. These alterations in the polypeptide scan profile of frost-killed needles were not caused by the low temperature treatment as such, but they occurred after thawing of the needles.     

Redescription of the clam shrimp Lynceus gracilicornis (Packard) (Branchiopoda, Conchostraca, Lynceidae) from Florida, with notes on its biology

Clam shrimps of the family 1.ynccidac differ markedly from all other families of the Conchostraca. The biology and morphology of the genus Lynceus are poorly known. In North America the genus is represented by four species: L. brachyurus, L. mucronatus, L. brevifrons and L. grarcilicornis. The last species, previously known from two localities in Texas, is reported from an ephemeral pond in north Florida. Amoung the characters distinguishing L. gracilicornis from North American congeners arc dimorphic male claspers and a broad, straight rostral margin. Females are distinct in having a smoothly rounded, distal rostra1 margin. External and internal morphology are described using light and scanning electron microscopy. Scanning electron microscopy reveals the presence of frontal setose sensory fields and a small rostral pit in both sexe5. Numerous setal types are described from the claspers and posterior thoracopods. Internal structures include a large anterior hepatopancreas, C-shaped gut and large paired gonads ventro-lateral to the gut.     

Arrhenius plots and the involvement of thermotropic phase transitions of the thylakoid membrane in chilling impairment of photosynthesis in thermophilic higher plants

Abstract Breaks and discontinuities in Arrhenius plots of physiological and physical properties of thylakoids are not diagnostic of thermotropic lipid phase transitions of the membrane. Bulk lipid transitions, as first inferred by the membrane phase transition hypothesis, do not occur in any higher plant at chilling temperatures. Solidification of some varying, but always minor, fraction of the total membrane lipid does take place. However, the presence of minor domains of solid thylakoid membrane lipid at chilling temperatures is not unique to chilling sensitive plants but is also found in tolerant species. Minor solidification may in some plants, or groups of plants, be controlled by the specific molecular species of phosphatidylglycerol only recently investigated. In plants containing little, or no, phosphatidylglycerol with this positional distribution of fatty acids, other yet unknown constituents of the membrane must fill a similar function, since DSC thermograms indicate minor solidification also in isolated, unperturbed thylakoids from chilling tolerant species. However, chilling induced phase transitions, or other perturbations, of the thylakoid membrane are not the reason for the chilling lability of net photosynthesis in the intact plant. This conclusion follows from detailed comparison between photosynthetic membranes isolated from prechilled plants and the effects of chilling exposure on CO₂ fixation of the whole plant. Damage at the level of the thylakoid membrane does occur, although not to the extent where it can account for the proportionally much larger damage to CO₂ fixation.     

PYRETHRUM CULTIVATION IN ENGLAND, 1925-37

Small plot and field experiments on the cultivation of the insecticidal pyrethrum plant in England during 1925-37 showed that the plant grew well and produced satisfactory yields of flowers of high pyrethrin content: costings of the field trials, however, showed that the cultivation of the plant was uneconomic. Individual plants grown from seed differed considerably in growth habit and in the pyrethrin content of their flowers.     

Rates of Progress towards Flowering and Podding in Bambara Groundnut (Vigna subterranea) as a Function of Temperature and Photoperiod

The influence of temperature and photoperiod on phenologicaldevelopment of three bambara groundnut (Vigna subterranea) selectionsfrom Botswana, Zimbabwe and Mali was investigated in a semi-controlledenvironment experiment with factorial combinations of threeconstant temperatures (20.9, 23.4 and 26.2 °C) and fourconstant photoperiods (10.0, 12.5, 13.5 and 16.0 h d^-1). Inall three selections, the onset of flowering was influencedby temperature but not by photoperiod, while the onset of pod-growth(‘podding’) of all three selections was influencedby both factors. The influence of temperature and photoperiodwas quantified by means of photothermal models, linking developmentrates to temperature and photoperiod with linear equations.The rate of progress from sowing to flowering of the three selectionscould be described very well (r²>95%) as a function of temperature;the rate of progress from flowering to podding was describedreasonably well as a function of both temperature and photoperiodby a combination of one to three response planes (r²for thedifferent selections ranging from 63 to 90%). Model testingwith independent data sets showed good agreement between observedand predicted times to flowering and podding. Vigna subterranea; Voandzeia subterranea; bambara groundnut; phenology; development; flowering; podding; photoperiod; temperature; modelling     

Cuticular hydrocarbon profiles as a taxonomic tool: advantages,limitations and technical aspects

Cuticular hydrocarbons (CHCs) are expressed on an insect's cuticle and are one of the major factors allowing insects to identify members of their own species, colony and gender. As a result of their species‐specificity, CHCs are increasingly used to delimit species in addition to more conventional methods, such as morphology or genetic markers, and so play an important role in chemotaxonomy. Species vary in the type of CHCs that they produce, as well as in the relative quantities of shared compounds. This review summarizes not only how taxonomists may differentiate between species based on CHC profiles, but also the incentive for using CHC composition as taxonomic tool. Benefits regarding the identification of cryptic species and early signs of reproductive isolation are then discussed, giving examples from studies of taxonomy, behaviour and biosynthesis. For taxonomic characters to reliably indicate species boundaries, their limitations need to be known. Potential problems caused by environmental effects, intra‐species variation in profiles and other technical issues are highlighted, and suggestions are made regarding their avoidance. It remains a challenge to determine the variation beyond which two species can be called independent; a problem shared by most methods of delimitation. Recently, there has been a shift towards using a combination of different taxonomic tools, both molecular and non‐molecular, to test observed species differences.     

SENSORY AND INSTRUMENTAL FLAVOR ANALYSES OF CHEESE CURD COCULTURED WITH SELECTED YEAST AND BACTERIA

Relationships between odor properties and volatile chemical composition were explored on 39 cocultures of three different yeasts, three Geotrichum candidum and five bacteria, commonly used in bacteria and mold surface ripened cheese. Sensory profiling was performed by ten trained judges by scoring the intensity of 14 odor attributes. At the same time, the volatile compounds of the cocultures were extracted and analyzed by dynamic headspace gas chromatography and mass spectrometry. Sensory and instrumental data were compared and correlated using correlation analysis and partial least squares regression analysis. The sample plot including the whole set of samples evidenced a clustering of the associations containing the yeast strain Kluyveromyces lactis and any bacteria. They developed strong fruity olfactory notes related to their high content of ethyl esters and various alcohols. The sample plot on a restricted set of samples evidenced the fruity characteristics of Debaryomyces hansenii and bacteria associations and the cheesy odors of Yarrowia lipolytica and Geotrichum candidum cocultures that produced sulfur compounds.     

The Bonobo–Dialium Positive Interactions: Seed Dispersal Mutualism

A positive interaction is any interaction between individuals of the same or different species (mutualism) that provides a benefit to both partners such as increased fitness. Here we focus on seed dispersal mutualism between an animal (bonobo, Pan paniscus) and a plant (velvet tamarind trees, Dialium spp.). In the LuiKotale rainforest southwest of Salonga National Park, Democratic Republic of Congo, seven species of the genus Dialium account for 29.3% of all trees. Dialium is thus the dominant genus in this forest. Dialium fruits make up a large proportion of the diet of a habituated bonobo community in this forest. During the 6 months of the fruiting season, more than half of the bonobos’ feeding time is devoted to Dialium fruits. Furthermore, Dialium fruits contribute a considerable proportion of sugar and protein to bonobos’ dietary intake, being among the richest fruits for these nutrients. Bonobos in turn ingest fruits with seeds that are disseminated in their feces (endozoochory) at considerable distances (average: 1.25 km after 24 hr of average transit time). Endozoochory through the gut causes loss of the cuticle protection and tegumentary dormancy, as well as an increase in size by water uptake. Thus, after gut passage, seeds are better able to germinate. We consider other primate species as a potential seed disperser and conclude that Dialium germination is dependent on passage through bonobo guts. This plant–animal interaction highlights positive effects between two major organisms of the Congo basin rainforest, and establishes the role of the bonobo as an efficient disperser of Dialium seeds. Am. J. Primatol. 75:394‐403, 2013. © 2013 Wiley Periodicals, Inc.